A paper published in Nature in Sept. 2023, reported about different Clostridium tetanus (tetanus) strains found in ancient archaeological remains, some of which included Chinchorro mummies. Their findings are interesting and may shed some light on the European DNA found in Chinchorro remains.
The authors studied the Clostridium tetani a microbe which produces a potent neurotixin that causes tetanus or "lockjaw" disease (the tetanus neurotoxin or TeNT). They identifed TeNT variants in South American archaeological remains, and one TeNT variant, extracted from a 6000-year-old Chinchorro mummy was still active, and provoked paralysis in mice.
Their data included samples from Japanese (3000 BP), Egyptian (3900 BP), Chinchorro remains (5900 BP). And modern samples too.
Normally you'd expect more divergence to be associated with older lineages, that evolved separately from others, over longer periods of time. The study reported "five strains (Sanganji-A2-Tooth, Chinchorro-Mummy-Bone, SLC-France-Tooth, Karolva-Tooth, Chincha-UC12-24-Tooth) were identified ... as possessing higher estimated levels of strain variation."
They measured the DNA damage in the bacteria samples to use it as an indicator of antiquity (more damage implies an older sample which has had more time to degrade), this also affects the human DNA and mtDNA.
But the researchers noticed that bacterial DNA had less damage than the mtDNA in the human tissue they came from. The authors interpreted this by assuming that less damage meant less age, implying that the tetanus and the humans carrying them were not contemporary: "damage rates were generally lower than the corresponding human mtDNA rates, especially for some samples (e.g., Tenerife-004, Tenerife-013, Chinchorro-Mummy-Bone), which may suggest that a subset of the archeological samples have been colonized by C. tetani at later dates." Notice it includes two samples from the Canary Islands, and the Chinchorro bone sample.
The ancient lineages are highlighted in bold font. And as expected, certain lineages cluster together, the "1H" lineage is found in ancient American samples while "2" lineages were Old World ones, and the "X" clade was found exclusively in Europe. We marked the Chinchorro samples with red arrows in the image above.
The authors point out that "Notably... the Sanganji, Tenerife, Chinchorro, and Chincha samples do not show evidence of branch shortening in the tree indicative of ancient genomes, and instead cluster with modern strains. These... tend to have higher rates of strain variation, which could affect branch lengths, or low damage rates potentially indicative of a more recent origin."
When they focused on the "tent" gene sequences they found that "The largest number of unique substitutions occurred in tent/Chinchorro... which is the oldest sample in our dataset [with] 18 unique substitutions not found in modern tent, and 12 of these are shared with tent/El-Yaral and 10 with tent/Chiribaya. The three associated acBins also cluster as neighbors in the phylogenomic tree ... and the three associated archeological samples originate from a similar geographic region in Peru and Chile ... suggest[ing] a common evolutionary origin for these C. tetani strains and their unique neurotoxin genes and highlight tent subgroup 3 as a distinct group of tent variants exclusive to ancient samples."
This is, in my opinon, proof of an ancient origin (hichly diverse, unique), and associated with variants that are found in ancient samples from the same geographical region in Peru and Chile.
However, the authors suspect that the tetanus varieties found in these samples are recent and came from the researchers who handled the remains or from the soil that was in contact with them. It is a good point:
"...a variety of environmental factors and mechanisms may account for the presence of toxigenic clostridia in aDNA samples. These include the possibility of their introduction by human handling of archeological samples by researchers, their introduction from human handlers during ancient mummy preparation practices, or post-mortem colonization by environmental (e.g., soil) clostridia. Regarding our identification of C. tetani in numerous mummy samples, it is worth mentioning that although today mummies are manipulated taking in consideration cross-contamination, during the 1990s when some of these mummies were first discovered, fieldwork procedures were different. Thus, it is notable that the Chinchorro mummy sample from which we identified the TeNT/Chinchorro toxin, was not always handled by researchers using nitrile gloves during digging; also, these mummies have been manipulated by many researchers since their initial discovery (B. Arriaza, Personal communication)."
But, how could have the samples from El Yaral and Chiribaya have a similar strain? Were the same researchers handling all of these bones? And, why aren't these strains of tetanus found in modern samples in the countries from which these researchers of the 1990s came from?
This 1H strain is a singularity, and the authors find it strange they note that only one modern sample (you can see it in the tree, in gray, as 2017.061) clusters with the American strains of Chichorro. It was found in France. How could an ancient Amerindian tetanus microbe appear in France?
The scientists explain this incongruity as follows: (aDNA = ancient DNA)
"Lineage 1H in particular has undergone the greatest expansion through the newly identified aDNA-associated C. tetani genomes, from one known sample derived from a patient in France in 2016 10, to 9 additional draft genomes assembled from ancient DNA. This suggests that a broader diversity of 1H strains may exist in undersampled environments. Interestingly, these newly identified lineage 1H strains share a common pattern of originating from the Americas, which suggests that a lineage 1H C. tetani strain specific to (or abundant within) this region may have colonized these samples at some point in the past."
Nevertheless, the ancient Amerindian samples "revealed novel variants and lineages of TeNT, including the newly identified “subgroup 3” toxins: TeNT/Chinchorro, TeNT/El-Yaral toxins, and TeNT/Chiribaya-Alta. Not only do these toxins share a similar mutational profile, but they are derived from a similar geographic area (regions of Peru and Chile in South America) and their associated C. tetani genomes also cluster phylogenetically as the closest neighbors... the tent/Chinchorro gene also happened to be most divergent from modern tent sequences by possessing the greatest number of unique substitutions. Despite being the most divergent tent, [it]... did not show strong patterns of DNA damage, and the damage level was weaker than that for human mtDNA. This indicates that, despite originating from the oldest sample in our dataset and possessing a unique tent variant, it is possible that the Chinchorro mummy-associated C. tetani strain may be a relatively “newer” strain that colonized the sample post-mortem."
Another paper, the one that identified the H1 variant in France, includes a tree (see its Figure 1), as can be seen, the only H1 sample detected is located on a separate branch that is distinct from all other branches A to G in Clade 1. This means an ancient origin, close to the root from which all these tetanus variants originated.
A recent paper, published this year studying botulism and tetanus, also reported "DNA damage patterns" and also found "that human mitochondrial DNA (mtDNA) exhibited significant damage ... consistent with expectations for degraded ancient DNA. However, the majority of toxin genes displayed minimal damage... This discrepancy suggests that most toxin genes in our dataset have undergone less degradation than the endogenous host DNA. "
They say that human handling, scavengers or soil contamination could have included younger bacteria into the samples, but also add a new suggestion: that the bacteria are more resistant to degradation. They stat that: "This may be due to differential DNA preservation (Clostridium spores may be more resistant to environmental degradation, leading to better long-term DNA preservation)." They suggest ways by which further studies could prove which factor causes this different degradation.
This 2025 study also indicates that TeNT "was also identified in aDNA from horses, wild bears, gorillas, and chimpanzees." However, I must add, that these animals were not found in Pre-Hispanic America, so they couldn't act as natural sources..
Let's hope that further research clarifies the degradation issue, and more information is gathered on the 1H variant and its distribution around the world.
Patagonian Monsters - Cryptozoology, Myths & legends in Patagonia Copyright 2009-2025 by Austin Whittall ©
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